A young mouse named Fievel and his family decide to migrate to America, a "land without cats," at the turn of the 20th century. But somehow, Fievel ends up in the New World alone and must fend off not only the felines he never thought he'd have to deal with again but also the loneliness of being away from home.

Some time after the Mousekewitz's have settled in America, they find that they are still having problems with the threat of cats. That makes them eager to try another home out in the west, where they are promised that mice and cats live in peace. Unfortunately, the one making this claim is an oily con artist named Cat R. Waul who is intent on his own sinister plan.

Follow the clues to fun and excitement as the beloved little mouse takes on a big monster in this charming, full-length adventure. When a ferocious, mouse-nabbing creature puts fear into the hearts of New York City's rodents, Fievel and his friends team up with a reporter to chase after the scoop of the century and -- just maybe -- get a close-up look at the bad guy himself!

Fievel and his friend Tony Toponi find a map that they believe points to a treasure buried somewhere beneath Old New York, and the plucky rodent is determined to find it. However, what he discovers under the city is a tribe of Native American mice who were driven underground by prejudiced European immigrants.

Peter-No-Tail (Pelle Svanslös) is a cat who was born without a tail. He compensates this by studying hard and, much to the dismay of his arch-rival Magnus (Måns), he receives a fancy university degree very few cats in the university town Uppsala, Sweden have obtained. Peter is visited by his American relative Pelle Swanson who invites him to visit his new home country America - in the movie called Americat. There everything is bigger and everything seems possible.